Welcome to the How-To section of our site. Here you should be able to find helpful hints & tips relating to working with mix-at-site concrete. To find out how Mixamate may be able to help you on a specific job, you can also find further information on our Services page.
Tools for the Job
Most homeowners will probably have most of the tools and materials required to lay ready mixed concrete, but it may help to check through the list below before you order.
- 2 wheelbarrows on each lorry
To ensure a good job is done you will need:
- Straight Edge – (for levelling)
- Rake – for moving concrete
- String – for setting out
- Tape measure
- Hammer and nails
- Float – for finishing surface
- Timber – for pegs, formwork and tamping beam
- Spirit level
- Wood saw
- Brush – for possible surface finish and cleaning up
Laying the Concrete
Spread the concrete between the formwork using a rake to distribute it evenly so that the top is about half an inch (15mm) higher that the required finish level.
Ensuring that all corners and edges are completely filled by treading the concrete in with the soles of your Wellington boots or by pushing it down with a piece of wood. Starting at one end use a heavy wooden tamping beam to compact the concrete, and move slowly along the slab removing any excess concrete. If necessary repeat this operation until the concrete is fully compacted and the surface is level with the top of the framework.
Finishing the Surface
Concrete can be left as tamped in which case the finish will depend on how carefully you tamp. Alternatively, there are a number of different surface finishes which can be produced after tamping.
A fine or coarse non-skid surface can be made by drawing a soft or hard sweeping brush across the surface of the concrete. Working a wooden float across the surface will give a textured surface which can be straight or circular design depending on how you move the float. A steel or plastic float will give a smooth finish.
As soon as the concrete has hardened enough not to be marked. it should be covered with polythene, weighted down at the edges, to stop it drying out too fast. The polythene can be removed after two or three days. Fresh concrete should not be allowed to freeze, so don’t lay when frost is likely unless you are prepared to insulate it with a 4 inch (100mm) layer of straw between two layers of polythene or a thermal blanket.
It is a common misconception that concrete should be left to dry out. THIS IS NOT TRUE! Especially on hot, dry, or windy days, it is important that the concrete be protected from drying too quickly, as this can cause cracking of the fresh concrete to occur.
A weighted down polythene sheet or tarpaulin stops the concrete drying too rapidly, and helps the material develop maximum strength.
Antifreeze for Concrete
There is no such thing as antifreeze for concrete, although you can put an accelerator into the mix which can be especially useful in winter. Follow the advice above with regard to keeping heat in for the first 24hrs.
A Good Job is Well Planned
Time spent in planning the job will be repaid many times during subsequent stages of the project. Start by sketching a plan to see how things will fit.
If you draw this to scale it will help you to calculate how much concrete you will need. Next set the job out on the ground. Use nails with pegs and string lines to ensure that things will finish as you intend them to.
All levels should be measured from a known point if possible. Don’t forget that any surface adjoining a building must be at least 150mm below the damp-proof course and should be laid to slope away from the building so that water drains away.
Levelling pegs, a spirit level on a piece of straight timber can be used over short distances, use a water level made from a clear plastic pipe filled with water.
Provided the pipe is carefully filled and has no air locks, the water at each end of the pipe will be exactly level. Large areas of concrete should have a fall of about 1 in 40 so that water runs off adequately. Set the high side first, then the low side.
Preparation (Bases and Drives)
All concrete needs to have a solid sub-base of adequate depth. Dig out the area to twice the required depth of concrete below the finished surface level. (For driveways or garage bases taking cars, the minimum thickness should be 100mm or 4″).
Once dug, compact the soil in the base with a garden roller or Wacker plate, then place and compact a layer of crushed stone or hardcore, leaving sufficient space for the depth of concrete required.
Set the formwork around the edge of the area and nail it solidly to firm pegs spaced at regular intervals along its length, ensuring that the pegs are on the outside of the boards.
Check that all levels and falls are correct, and that pegs do not project above the formwork. Measure the depth, width and length in metres and multiply these together to determine the volume of concrete in cubic metres that you need to order. I.e. 3m x 4m x .100 = 1.2 metres cubed or please visit our concrete calculator. If you prefer to work in yards and inches, measure the width and length in yards and multiply together to give you the area in square yards.
Alternativelty, if you need help in calculating the amount you need give Mixamate’s helpful staff a ring and they will gladly work out how much concrete you need.
Ask us about our Mini Dumper service to aid replacement of your Concrete and Screed.